_Atropos pulsatorius_ is one of these. It lives in books and among old damp papers, whence it is often called the "Book Louse." [Illustration: Fig. 57.--Perla Bicaudata.] [Illustration: Fig. 58.--Psocus Bipunctatus.] They are also very destructive to collections of preserved insects and plants. About thirty species occur in this country. _Family 6, Embiidæ._--This family contains no representative in the British Isles, and consists of a small number of almost exclusively exotic species. Two species, however, inhabit the continent of Europe, one of which, _Embia Solieri_, occurs in the south of France on the Mediterranean littoral. These insects are very closely allied to the _Psocidæ_ in their habits. TRIBE V.--SOCIALIA. The Socialia contains a very peculiar group of insects closely allied to the cockroaches in the _Orthoptera_. They may be considered a connecting link between that order and the Neuroptera. There is only one family. _Family 7, Termitiæ._--The _Termitiæ_, or White Ants, are almost exclusively inhabitants of tropical climates, and are unrepresented in our own country. They are a very remarkable family of insects. They build most complicated dwellings, consisting of innumerable galleries and chambers, and they are so interesting in their habits that every traveller who has seen anything of them has always a great deal to relate concerning them. One species, _Termes lucifugus_, inhabits the south of France, and is very well known on account of the mischief which it sometimes causes. [Illustration: Fig. 59.--Termes Bellicosus (Male).] [Illustration: Fig. 60.--Termes Bellicosus (Soldier).] TRIBE VI.--PHYSOPODA, OR THRIPS. This tribe of insects, to which the name _Thysanoptera_ is sometimes applied, contains many curious forms. There are two principal groups of these insects--namely, the _Tuberlifera_ and the _Terebrantia_. They are generally known to gardeners by the name of "Thrips." Some of them occasionally prove injurious to cultivated plants. This is especially the case with the Corn Thrips (_Thrips cerealium_), which generally attacks the ears of corn, and, when numerous, is very mischievous. TRIBE VII.--MALLOPHAGA OR BIRD LICE. These insects, which are known as "Bird Lice," were formerly placed among the true lice, but they differ in the possession of biting mouths, and in the diet to which such a structure adapts them. A great number of these curious little insects have been recorded, and they inhabit all parts of the world. They live among the feathers of birds and the hairs of mammalia. Almost every animal and bird is subject to these parasites. The common fowl, duck, goose, game birds of all kinds, and pigeons, are very commonly infested by them, as are also the dog, the cat, the sheep, and the guinea-pig. The two principal families of the _Mallophaga_ are the _Philopteridæ_ and the _Liotheidæ_. [Illustration: Fig. 61.--Lipeurus Diomedeæ (Mag.)] TRIBE VIII.--THYSANURA OR BRISTLE TAILS.